Microelectromechanical structures (MEMS) and other microengineered devices are presently being developed for a wide variety of applications in view of the size, cost and reliability advantages provided by these devices. Many different varieties of MEMS devices have been created, including microgears, micromotors, and other micromachined devices that are capable of motion or applying force. These MEMS devices can be employed in a variety of applications including hydraulic applications in which MEMS pumps or valves are utilized and optical applications that include MEMS light valves and shutters.
MEMS devices have relied upon various techniques to provide the force necessary to cause the desired motion within these microstructures. For example, cantilevers have been employed to transmit mechanical force in order to rotate micromachined springs and gears. In addition, some micromotors are driven by electromagnetic fields, while other micromachined structures are activated by piezoelectric or electrostatic forces. Recently, MEMS devices that are actuated by the controlled thermal expansion of an actuator or other MEMS component have been developed. For example, U.S. patent application Ser. Nos. 08/767,192; 08/936,598, and 08/965,277 are assigned to MCNC, the assignee of the present invention, and describe various types of thermally actuated MEMS devices. In addition, MEMS devices have been recently developed that include rotational connections to allow rotation with less torsional stress and lower applied force than found with torsion bar connections. For instance, U.S. patent application Ser. No. 08/719,711, also assigned to MCNC, describes various rotational MEMS connections. The contents of each of these applications are hereby incorporated by reference herein.
Thermally actuated MEMS devices that rely on thermal expansion of the actuator have recently been developed to provide for actuation in-plane, i.e. displacement along a plane generally parallel to the surface of the microelectronic substrate. However, these thermal actuators rely on external heating means to provide the thermal energy necessary to cause expansion in the materials comprising the actuator and the resulting actuation. These external heaters generally require larger amounts of voltage and higher operating temperatures to affect actuation. For examples of such thermally actuated MEMS devices see U.S. Pat. No. 5,881,198 entitled "Microactuator for Precisely Positioning an Optical Fiber and an Associated Method" issued Mar. 9, 1999, in the name of inventor Haake, and U.S. Pat. No. 5,602,955 entitled "Microactuator for Precisely Aligning an Optical Fiber and an Associated Fabrication Method" issued Feb. 11, 1997, in the name of inventor Haake.
As such, a need exists to provide MEMS thermal actuated devices that are capable of generating relatively large displacement, while operating at significantly lower temperatures (i.e. lower power consumption) and consuming less area on the surface of a microelectronic substrate. These attributes are especially desirable in a MEMS thermal actuated device that provides relatively in-plane, linear motion and affords the benefit of having a self-contained heating mechanism.